In numerical simulation of spray combustion using kerosene, the validity of using water in spray experiments to determine the size distribution of spray droplets and the effect of the size distribution on the calculated spray combustion characteristics were investigated. The effect of parcel number on the combustion behavior was also discussed. A 20 wt% ethanol solution was used as a substitute for kerosene because its physical properties are similar to those of kerosene. Although the droplet diameters of water spray are larger than those of ethanol solution spray, the difference has little influence on combustion characteristics. The calculated temperature distribution using a small number of parcels (=450) is similar to that using a large number of parcels (=450,000), but they differ in the upstream region. Recently, further reduction of NOx and soot emission is required. Therefore, to predict NOx and soot concentration more accurately, it is important to calculate the exact temperature distribution especially in the upstream. The calculated results indicate that a parcel number of at least 4500 is needed to carry out accurate spray combustion calculation when a pneumatic atomizer is used in the combustor.